ADAM15 is a transmembrane glycoprotein characteristic of disintegrin metalloprotease with the ability to shed receptor molecules and regulate cell-cell/matrix adhesions. Increased ADAM15 expression is associated with the development of metastatic cancer, atherosclerosis, and inflammatory bowl disease. Our recent work has identified a novel function of this molecule as a pro-inflammatory factor capable of increasing vascular endothelial permeability. Further studies suggest that ADAM15 is upregulated in the lungs during bacterial infection or septic stimulation, contributing to neutrophil infiltration and pulmonary edema. The tissue-specific effect and underlying mechanisms of ADAM15-mediated barrier injury have not been characterized. The overall goal of this project is to understand the molecular control of ADAM15 expression and function in inflammation. Two specific aims are proposed: 1) to characterize the functions and regulatory pathways of ADAM15 activity in sepsis, and 2) to elucidate the molecular mechanisms by which ADAM15 induces hyperpermeability. The central hypothesis to be tested is that sepsis induces ADAM15 upregulation at the transcriptional and posttranslational levels. ADAM15 increases endothelial cell-cell junction permeability by activating Src signal transduction via its cytoplasmic domain, whereas disintegrin regulation of focal adhesions and/or metalloprotease shedding of junctional structures serve as alternative pathways. This novel concept will be validated through a series of complementary studies that integrate in vivo physiological analyses using animal models and in vitro molecular assays in cultured cells. Innovative experimental models and molecular tools will be constructed and tested. Data derived from the proposed work will not only establish a novel theory in protease molecular biology, but also provide new mechanistic insights into the pathophysiology of sepsis and acute inflammation. In addition, the study has potential impact on the identification and development of novel therapeutic targets for effective treatment of inflammatory disease. PUBLIC HEALTH RELEVANCE: Systemic inflammatory injury is a major cause of mortality and morbidity in patients with sepsis, which affects more than 750,000 Americans annually. Despite the advanced theories regarding its pathogenesis, there has been no major breakthrough in treatment or prevention. The limited clinical progress is partially attributed to the underdevelopment of effective therapies, owing to the complexity of the disease and our incomplete understanding of its endpoint cellular mechanisms. Increased microvascular permeability represents a common endpoint of inflammatory response to various types of injury. Endothelial barrier dysfunction causes plasma leakage and leukocyte infiltration in vital organs, especially in the lungs, leading to respiratory distress and multiple organ failure. The essential role of endothelial barrier injury in acute systemic inflammation highlights the need to develop target-directed treatments. The proposed work is important because it will provide novel mechanistic insights into the molecular control and physiological regulation of endothelial barrier function under clinically relevant septic conditions. In addition, the study has potential impact on the identification and development of new therapeutic targets for improved treatment and prevention of inflammatory injury.